Women and Infants Transmission Study (WITS), the purpose of which is to begin to understand how often HIV is passed on to children of risk mothers; to make early diagnosis; to understand how children with HIV infection grow and develop; and to allow early intervention as therapies become available. Currently, 82 infants and children are actively followed in WITS at Children's Hospital. A number of findings over a broad spectrum of disciplines has begun to emerge from the WITS study. The preliminary findings are interesting and may possibly be useful for counseling pregnant women. The following are research areas resulting from WITS: 1) obstetrical factors which influence HIV-1 transmission; 2) immunologic and virologic correlates of vertical transmission; 3) use of dried blood spot specimens and the diagnostic value of PCR for detection of HIV, and 4) natural history of somatic growth in infants born to HIV infected women.